Method for manufacturing sintered body for forming sintered magnet, and method for manufacturing permanent magnet using sintered body for forming sintered magnet

Abstract

Provided are: a method for manufacturing a sintered body as a base of a sintered magnet and a method for manufacturing a permanent magnet. Specifically, a magnet raw material is pulverized into magnet powder, the magnet powder pulverized and a binder are mixed, thereby to form a compound. The, a formed body, obtained by forming the compound formed, is sintered by heating up the same to a firing temperature in a pressed state at a predetermined heat-up rate, and by keeping the same at the firing temperature. In the sintering step, the pressure value for pressing the formed body is set to: less than 3 MPa from the start of heating up of the formed body to a predetermined timing during heating up of the formed body; and 3 MPa or more after the timing.

1 . A method for manufacturing a sintered body as a base of a sintered magnet, comprising:
 a heating step of heating a formed body obtained by forming magnet powder to a firing temperature; and   a sintering step of sintering the formed body,   wherein the formed body is kept under pressure at a pressure value of less than 3 MPa at a start of the heating step until a predetermined timing, and 3 MPa or more after the predetermined timing.   
     
     
         2 . The method for manufacturing according to  claim 1 , wherein the predetermined timing is any timing when a temperature of formed body is in a range of 300° C. to 900° C. 
     
     
         3 . The method for manufacturing according to  claim 1 , wherein the predetermined timing is a timing when the magnet powder contained in the formed body begins to fuse. 
     
     
         4 . The method for manufacturing according to  claim 1 , wherein a temperature of the formed body is raised and maintained at 900° C. or higher after the predetermined timing. 
     
     
         5 . The method for manufacturing according to  claim 1 , wherein a maximum value of the pressure value after the predetermined timing 30 MPa. 
     
     
         6 . The method for manufacturing according to  claim 1 , wherein in the sintering step, a heat-up rate of the formed body is 20° C./min or higher. 
     
     
         7 . The method for manufacturing according to  claim 1 , further comprising a step of subjecting the magnet powder to magnetic field orientation by applying a magnetic field to the formed body, wherein in the sintering step, the formed body is pressed in a direction perpendicular to a direction of the magnetic field orientation of the magnet powder. 
     
     
         8 . The method for manufacturing according to  claim 1 , wherein the formed body is obtained through a debinding process of a green body formed of a mixture containing magnet powder and a binder. 
     
     
         9 . A method for manufacturing a permanent magnet, comprising a step of magnetizing the sintered body as a base of a sintered magnet, manufactured by the method for manufacturing according to  claim 1 .